PEO-based Block Copolymer Membranes:Multiscale Structure Regulation And Enhancement Of CO₂ Separation Performance

At present,the development of carbon capture technology is an inevitable requirement to solve the greenhouse effect.As one of the carbon capture technologies with great development potential,membrane technology has the advantages of energy saving,high efficiency and environmental protection.Therefore,as the core of membrane technology,improving the separation performance of membrane materials is an important goal of the research.In this paper,based on the solution-diffusion characteristics of gas in polymer film,the structure of membrane was precisely tuned by varying scales through the way of hybridization.Therefore,high CO₂/N₂ separation performance was achieved.The details were summarized as follows:?1?Polymer electrolyte membrane was fabricated by doping betaine?one kind of zwitter-ion?and Polyethyleneglycol dimethyl ether?PEGDME?.At humidified state,the synergy of water and zwitter-ion remarkably intensified solution-diffusion mechanism simultaneously.On one hand,anion of betaine?carboxylate ions?can improve the hydration and dissociation of CO₂,while kation?quaternary amine?could transport the dissociated HCO₃^-to downstream of membrane in time,which realized efficient CO₂ separation.On the other hand,the addition of betaine increased the total amount of absorbed water and CO₂ permeability increases almost linearly with the increase of water content in membranes.As a consequence,the as-prepared membrane showed the highest CO₂ permeability of 637 Barrer and CO₂/N₂ selectivity of 86,150%,100%higher than those of neat Pebax membrane,respectively.The separation performance of membrane has distinct improvement compared with above research.?2?Polydopamine/polyethylene glycol?PEG?composite microcapsules were synthesized by hard template method for the modification of Pebax matrix to prepare mixed matrix membranes?MMMs?.Polydopamine in the wall of the capsule can generate strong polymer-filler interface adhesion,avoiding the degradation of separation performance caused by the interface incompatibility between the filler and the matrix.Through the analysis of the pore structure,the template removal process produces through-wall mesopores,which allow rapid gas diffusion into the lumen,further significantly reducing the trans-membrane mass transfer resistance.The remaining PEG in the capsule wall not only increases CO₂ affinity,but also avoids excessive chain rigidification at polymer-filler interface.In this way,the composite capsules,compared with those without PEG,confer significantly enhanced separation performance on membranes.The optimal gas transport property of the resultant membranes is obtained with a CO₂ permeability of 510 Barrer and an ideal selectivity of 84.6 for CO₂/N₂ at humidified state,i.e.,108%,98%higher than those of neat Pebax membrane,respectively.In addition,owing to dopamine-enabled strong adhesion,the MMMs exhibit better stability than Pebax membrane in the long-term test at 85°C.